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Thread: I'm new, the pool looks good, and CYA is high. Do I really need to replace the water?

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    I'm new, the pool looks good, and CYA is high. Do I really need to replace the water?

    Hi all,
    I'm a new home and pool owner. We had the pool professionally opened and the guys told me I need to shock it once a week. That sounded funny and I found your website and did some research. New plan - we are getting rid of the pool guys and DIYing (with your help).

    So our pool was opened about 1 month ago. It has looked good since day 4. The last time any chemicals were added were those pucks in the floating doodads. Those are now empty.

    Pool looks awesome and feels great to swim in.

    I tested today and this is what I got (Taylor 2005 + FAS-DPD)
    Taylor 2005 FC 6 TC 10 CC 4 (calculated)
    FAS-DPD FC 5.6 CC 0.5
    pH 7.6
    TA 100
    CH 210
    CYA 100

    Pool Math is telling me to drain 1/2 the volume of the pool and refill. It is also telling me to add chlorine up to a level of 8.

    Any advice/confirmation would be greatly appreciated before I make moves that involve 18,500 gallons of water.
    37,000g IG Painted Gunite
    Pentair Nautilus Plus NSP 72sq ft filter
    Taylor K2005 Test kit + FAS-DPD add-on
    Polaris robot thingy

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    Mod Squad tim5055's Avatar
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    Re: I'm new, the pool looks good, and CYA is high. Do I really need to replace the wa

    Welcome to TFP!

    If your CYA is really 100, then your chlorine is too low. The minimum FC ever should be is 7.5% of your CYa level, meaning CYA 100 = FC 7.5 minimum.

    The worse news is that 100 is the limit of the test. So, you could be 100, 150 or, 200; we just don't know. Water replacement is how you lower CYA, so that is what is really ahead of you.

    For now, get some plain old generic bleach in the pool to bring the FC up while you figure your next move.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: I'm new, the pool looks good, and CYA is high. Do I really need to replace the wa

    I have a couple of huge buckets of Cal-Hypo 73% granules that the pool company charged me for already. Is it ok to use that? Pool math says to use 1lb to get up to FC 8
    37,000g IG Painted Gunite
    Pentair Nautilus Plus NSP 72sq ft filter
    Taylor K2005 Test kit + FAS-DPD add-on
    Polaris robot thingy

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    Re: I'm new, the pool looks good, and CYA is high. Do I really need to replace the wa

    Quote Originally Posted by tim5055 View Post
    Welcome to TFP!

    If your CYA is really 100, then your chlorine is too low. The minimum FC ever should be is 7.5% of your CYa level, meaning CYA 100 = FC 7.5 minimum.

    The worse news is that 100 is the limit of the test. So, you could be 100, 150 or, 200; we just don't know. Water replacement is how you lower CYA, so that is what is really ahead of you.

    For now, get some plain old generic bleach in the pool to bring the FC up while you figure your next move.

    CYA may be much higher as mentioned above. Pool stores tested mine at 115 but after doing the dilution tests, was actually 350!
    18,000 gunite pool/spa combo. Pebble tec, iaqualink rs8, cl580 filter, aquapure 1400, 400k btu lx heater, 10 solar panels, jandy 1hp, 1 1/2hp, and 2hp stealth pumps for circ, spa, waterfall

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    Re: I'm new, the pool looks good, and CYA is high. Do I really need to replace the wa

    Ok. I repeated the test and we are definitely less than 100. Probably more like 90-95. I had a second set of eyes this time. My plan is to add 16 oz of cal-hypo 73% and let circulate then test again in AM.


    37,000g IG Painted Gunite
    Pentair Nautilus Plus NSP 72sq ft filter
    Taylor K2005 Test kit + FAS-DPD add-on
    Polaris robot thingy

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    Re: I'm new, the pool looks good, and CYA is high. Do I really need to replace the wa

    I had a CYA of 220, drained 1/2 to get to 110ish, and then just allowed the auto-drain / auto-fill + rain to dilute it. Note that evaporation is taking out water, but not CYA, so that won't do the trick. It needs to be exchanged. However, rain would overfill the pool and auto-drain helped trickle it down to 90. I was able to reduce chlorine demand accordingly. A few months and a LOT of rain later....I'm at 70.

    I managed 110, just cost a bit more. I managed 90 with little less effort. I maintain 70 pretty easily. I'll enjoy 50 when I finally get there. I only did 1 major drain, that as 1/2 the pool to get from 220 > 110. I let slow auto-drain / rain / auto-fill exchange the rest.
    Lee Mims - Orange, TX, 25400 gallon In-Ground Plaster Pool
    Hayward Cartridge Filter, Hayward Chlorine Feeder, Century 1081 2-Speed Pool & Spa Pump, Hayward H350FDN (350k BTU) Natural Gas Water Heater, Paramount O3 Ozone, Hayward Super II Pump for Waterfall, Aqualink RS System w/ Remote (Jandy), Taylor K-2006 Kit

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    Re: I'm new, the pool looks good, and CYA is high. Do I really need to replace the wa

    You can use the cal-hypo, just keep an eye on your CH number.
    8,500gal plaster in-ground with attached spa, two floor drains, one skimmer. Chlorine, City Water.
    Pentair WhisperFlo 1hp Pump, MagnaTek Midcentury EPlus motor, Pentair CleanNClear 200SF Cartridge filter, Purex Triton MiniMax 250 Gas Heater, Pentair SunLite, AutoFill.
    Kreepy Krauly Cruiser, TF-100 with SpeedStir. :D

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    Re: I'm new, the pool looks good, and CYA is high. Do I really need to replace the wa

    Might want to check the cal hypo to be sure it doesnt have stabilizer in it (most do) and will make cya problem even worse. Straight liquid bleach is pretty cheap and has no stabilizer.

    with stabilizer near 100 you need to maintain 12ppm FC and will require > 40ppm if you want to shock it.
    18,000 gunite pool/spa combo. Pebble tec, iaqualink rs8, cl580 filter, aquapure 1400, 400k btu lx heater, 10 solar panels, jandy 1hp, 1 1/2hp, and 2hp stealth pumps for circ, spa, waterfall

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    Re: I'm new, the pool looks good, and CYA is high. Do I really need to replace H2O?

    Quote Originally Posted by fajitas21 View Post
    I had a CYA of 220, drained 1/2 to get to 110ish, and then just allowed the auto-drain / auto-fill + rain to dilute it. Note that evaporation is taking out water, but not CYA, so that won't do the trick. It needs to be exchanged. However, rain would overfill the pool and auto-drain helped trickle it down to 90. I was able to reduce chlorine demand accordingly. A few months and a LOT of rain later....I'm at 70.

    I managed 110, just cost a bit more. I managed 90 with little less effort. I maintain 70 pretty easily. I'll enjoy 50 when I finally get there. I only did 1 major drain, that as 1/2 the pool to get from 220 > 110. I let slow auto-drain / rain / auto-fill exchange the rest.
    What do you mean by auto-drain/auto-fill? How do I know if this is going on?
    I am away for the weekend so I raised FC to 8 this morning and will be back tomorrow night to check and add more. I won't have a chance to buy liquid chlorine until Monday...
    37,000g IG Painted Gunite
    Pentair Nautilus Plus NSP 72sq ft filter
    Taylor K2005 Test kit + FAS-DPD add-on
    Polaris robot thingy

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    Re: I'm new, the pool looks good, and CYA is high. Do I really need to replace the wa

    Some of us have systems in our pools that add water when the water level drops below a certain point, and has a drain that will drain off water if the water level goes above a certain point. That's what fajitas meant.
    8,500gal plaster in-ground with attached spa, two floor drains, one skimmer. Chlorine, City Water.
    Pentair WhisperFlo 1hp Pump, MagnaTek Midcentury EPlus motor, Pentair CleanNClear 200SF Cartridge filter, Purex Triton MiniMax 250 Gas Heater, Pentair SunLite, AutoFill.
    Kreepy Krauly Cruiser, TF-100 with SpeedStir. :D

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    Re: I'm new, the pool looks good, and CYA is high. Do I really need to replace the wa

    How would I know if I have that kind of system?


    37,000g IG Painted Gunite
    Pentair Nautilus Plus NSP 72sq ft filter
    Taylor K2005 Test kit + FAS-DPD add-on
    Polaris robot thingy

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    Re: I'm new, the pool looks good, and CYA is high. Do I really need to replace the wa

    If it's built into the pool, it's often in a well about the size of a skimmer, but with a small hole below the waterline for the fresh water to enter the pool. There are liked a few other types, though. Generally, if you have to add water into your pool from time to time, you don't have one.
    8,500gal plaster in-ground with attached spa, two floor drains, one skimmer. Chlorine, City Water.
    Pentair WhisperFlo 1hp Pump, MagnaTek Midcentury EPlus motor, Pentair CleanNClear 200SF Cartridge filter, Purex Triton MiniMax 250 Gas Heater, Pentair SunLite, AutoFill.
    Kreepy Krauly Cruiser, TF-100 with SpeedStir. :D

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